PROJECT SUMMARY In this F31 proposal resubmission, I use novel synthetic transcription factors (TFs) delivered to the mouse medial prefrontal cortex (PFC) to uncover and manipulate the brain molecular processes that govern complex social behaviors. Social behaviors are central to the health of society and the individual, and are disrupted in a number of psychiatric illnesses. However, the neurobiological origins of social behaviors are incompletely understood. Here, I present synthetic biology approaches to re-program the function of ZFP189, a Kruppel-associated box (KRAB) zinc finger TF whose expression and function in the mouse PFC was previously determined to be protective against stress-induced social deficits. To interrogate gene targets and nuanced behaviors controlled by ZFP189, my laboratory and I developed novel synthetic ZFP189 TFs, each capable of exerting distinct forms of transcriptional control at in vivo ZFP189 target genes. We replaced the endogenous repressive KRAB moiety of ZFP189WT with a synthetic transcriptional activator in ZFP189VPR. Viral delivery of these synthetic TFs allows me to knowingly augment ZFP189-mediated transcription in the PFC of awake and behaving mice. In data presented in this application, I observe that virally delivering ZFP189VPR to the PFC of mice ablates social behaviors, without other observable behavioral deficits. By performing RNA sequencing (RNAseq) on manipulated tissues, I identify that the ZFP189 TFs of opposing function exert divergent impact on genes relating to adaptive immune response. These preliminary findings are in agreement with earlier published work proposing a co-evolutionary link between social behavior and the molecular cascades associated with anti-pathogen response in PFC pyramidal neurons. Other published evidence suggests that KZFPs bind repetitive DNA elements, including transposable elements (TEs), with are self-replicating sequences of DNA. My data shows that some of the transcripts most activated by ZFP189VPR are TEs. Based on my data and previous literature, I believe ZFP189 represents an evolutionally ancient link between regulation of brain TEs and the immune cascades that drive pro-social behaviors. Completion of this project will resolve the impact of synthetic ZFP189 TFs in governing social behaviors and social cognition necessary to function in a social group (Aim 1). Additionally, this project will illuminate the brain transcriptional mechanisms regulated by ZFP189 by performing RNAseq of virally manipulated PFC tissues (Aim 2). Together, this work will provide new approaches to identify the TF functions and illuminate the molecular origins of complex social behaviors. The skills I develop through this project and fellowship will position me for a competitive and successful career as a scientist.